The safest cities. The best cities. The happiest cities. We see the rankings all the time. But do they matter. Yes, says Samuel Arbesman, who surveyed 310 US residents by using Amazon's Mechanical Turk service.

At least, the favorite town of Outside Magazine's readership, in a survey of almost 22,000 readers. Outside says the factors that make Chattanooga hot range from "epic singletrack to progressive city planning."